1. Field of the Invention
This invention relates to a process for the production of lactide in which highly pure lactide usable as a raw material for the synthesis of a polyacetic lactic acid can be industrially produced at low cost.
Although highly pure lactide has heretofore been produced by using lactic acid as the starting material, a salt of a 2-halopropionic acid is used in place of lactic acid in the process of the present invention.
2. Description of the Prior Art
Usually, lactide is produced by heating lactic acid at about 200.degree. C. at a pressure of 20 mmHg or less to condense it with the elimination of water. Since readily obtainable lactic acid is used as the starting material, this process is often employed to synthesize a labo-use amount of lactide. However, this process must be carried out in a relatively high vacuum and, moreover, the reaction rate is low. Accordingly, high equipment costs will be required in order to carry out this process on an industrial scale. Furthermore, highly pure lactic acid will be required in order to produce highly pure lactide according to this process. A high degree of purification of lactic acid, in turn, will require considerable purification costs. For these reasons, it has been difficult to produce lactide of polymer grade industrially at low cost.